Well, its the usual suspects I'm afraid - a mix of small evergreens, some ivy and pansies or the smaller violas. The garden centres usually have small versions (rooted cuttings from earlier this year or last year) of various evergreens - small conifers, skimmias, euonymus aureus, osmanthus delaveyi, euonymus microphyllus, that kind of thing, and a fair bit of variegated colour can be achieved with those. The yellow and green variegated plants go well with Ophiopogon nigrescens, which remains evergreen and can provide a striking contrast with those and brightly coloured pansies. Acorus is a grass that will look fine all winter, so small sections of that can be used too. Unfortunately, when the weather is really cold, the pansies/violas stop flowering and just bide their time till it warms up a bit. One other bit of advice - buy the pansies/violas with larger rootballs, specially if its already late September when you get them - they aren't going to get any bigger till next spring, so using smaller plug type plants isn't advisable.

There are also available the small bedding type cyclamen, but in colder parts of the country, they often keel over by Christmas.